Nghiên cứu khả năng xử lý paraquat và DDT trong môi trường nước bằng vật liệu nano tio2 pha tạp fe, co, ni tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY …… ….***………… NGUYEN MANH NGHIA STUDY ON THE POSSIBILITY OF TREATMENT PARAQUAT AND DDT IN WATER ENVIRONMENT USING Fe, Co, Ni DOPED TiO2 NANO MATERIAL Major: Environmental Technology Code: 9.52.03.20 SUMMARY OF DOCTORAL THESIS IN ENVIRONMENTAL TECHNOLOGY Hanoi - 2019 The thesis has been completed at: Institute for Environemtal Technology – Graduate university science and technology – Vietnam Academy of Science and Technology Science supervisor: Assoc Prof Dr Nguyen Thi Hue Reviewer 1: Reviewer 2: Reviewer 3: The thesis was defended at National level Council of Thesis Assessment held at Graduate University of Science and Technology – Vietnam Academy of Science and Technology at….on…… Thesis can be futher referred at: -The Library of Graduate University of Science and Technology -National Library of Vietnam LIST OF PUBLICATIONS Nguyen Manh Nghia, Nguyen Thi Hue, Ma Thi Anh Thu, Phung Thi Len, Vu Thi Thu, Tran Dai Lam, Preparation and Characterization of Fe-Doped TiO2 Films Covered on SiO2, Journal of Electronic Materials, 2016, 45(7), 3795–3800 Nguyen Manh Nghia, Nguyen Thi Hue, Study on photocatalytic properties of Fe-doped TiO2 coated on silica-gel, JOURNAL OF SCIENCE OF VNU, 2016, 32(4), 24-29 Phung Thi Len, Nguyen Manh Nghia, Nguyen Cao Khang, Duong Quoc Van and Nguyen Thi Hue, Enhanced photocatalytic efficiency of TiO2 by doped Ni- immobilized on SiO2, JOURNAL OF SCIENCE OF HNUE, Mathematical and Physical Sci., 2016, 61(7), 151-156 Dang Xuan Thu, Vu Quoc Trung, Nguyen Manh Nghia, Nguyen Cao Khang, Tran Dai Lam, Effects of Fe Doping on the Structural, Optical, and Magnetic Properties of TiO2 Nanoparticles, Journal of Electronic Materials, 2016, 45(11), 6033–6037 Nguyen Thi Thanh Hai, Nguyen Manh Nghia, Nguyen Thi Hue, Nobuaki Negishi, Photocatalytic degradation of formic acid in aqueous with Ni doped TiO2 coated on SiO2, 2017, Vietnam Journal of Science and Technology 55 (4C), 174-179 Nguyen Manh Nghia, Nobuaki Negishi, Nguyen Thi Hue, Enhanced Adsorption and Photocatalytic Activities of Co-Doped TiO2 Immobilized on Silica for Paraquat, Journal of Electronic Materials, 2018, 47(1), 692–700 Tran Thi Minh Phuong, Nguyen Manh Nghia, Nguyen Thi Hue, Evaluate Photocatalytic Activities of Ni doped TiO2 coated on SiO2, Tạp chí Phân tích Hóa, Lý Sinh học, 2018, 23 (1), 66-72 Le Dien Than, Ngo Sy Luong, Vu Dinh Ngo, Nguyen Manh Tien, Ta Ngoc Dung, Nguyen Manh Nghia, Nguyen Thai Loc, Vu Thi Thu, Tran Dai Lam, Highly Visible Light Activity of Nitrogen Doped TiO2 Prepared by Sol–Gel Approach, Journal of Electronic Materials, 2017, 46(1), 158-16 INTRODUCTION Insecticides, fungicides, herbicides in our country are mostly imported, semiauthorized, packaged and then marketed to farmers Vietnam is importing these chemicals from countries such as China, Germany, Japan, Switzerland, USA, India, Taiwan, Singapore, Thailand Mostly from big chemical companies are Syngenta, Mosanto, Baier, Du-pont, etc The volume of chemicals imported has increased ten times in the last 10 years, while the area of agricultural land has not increased Pesticides, fungicides and herbicides are used in most agricultural practices such as growing rice, maize, potatoes, cassava, The most commonly used herbicides and herbicides are Paraquat and DDT, which play an important role in ensuring crop yields But, nowadays, these are abuse, dependence and misuse when farmers use these high toxic chemicals commonly in crops Paraquat is fast acting and kills the tissues of the grass when exposed It is used extensively throughout the world due to its high water solubility, high herbicides and low cost, however, it is very toxic to animals and humans Due to over-use and widespread use, it has caused great consequences to the quality of the surface water and soil environment Meanwhile, people in some mountainous areas in the North such as Hoa Binh and Ha Giang still use spring water, which is the main source of water for living and dining purposes DDT is a persistent, persistent chemical that has been banned for years, but its effects remain long-term For treatment of Paraquat (PQ) and DDT, catalytic, adsorption, and biological technologies have been used However, these post-processing methods often leave unwanted by-products, which are costly to invest Therefore, the development of environmentally friendly methods for treating polluted water with PQ is a matter for research to ensure the health of animals and humans To solve these problems, some advanced technologies, such as advanced oxidation (AOP), was applied in decomposing organic pollutants, including photocatalysts using materials nano Titandioxide (TiO2) Anatase TiO2 is non-toxic, low cost, and high catalytic activity However, pure TiO2 has a large band gap (3.2 eV), hence photocatalytic activity is stimulated by ultraviolet radiation which is very small ( Co- TiO2/SiO2 > Ni- TiO2/SiO2 - Has found that under the influence of natural light, paraquat was completely oxidized to NO3 - when using TiO2/SiO2 doped Co, whereas DDT was almost unaffected - Has successfully decompose herbicides (representative of Paraquat) and pesticides (representative of DDT) in surface water in real surface water using TiO2/SiO2 doped Co under Solar light Water after treatment reached QCVN 8: 2011 / BTNMT The structure of the thesis The thesis consists of 106 pages with 12 tables, 56 figures, 143 references The thesis was composed of pages, 28 pages of literature review, 18 pages of research subjects and methods, 54 pages of research results and discussion, conclusion of pages Chapter CHAPTER 1: LITERATURE REVIEW Compiled documents on: i) Current status of Paraquat and DDT pollution in the water environment in the world and in Vietnam; ii) Methods of treatment Paraquat, DDT; iii) pure TiO2 and doped TiO2; iv) Methods of fabrication TiO2 nanoparticles coated on carrier materials Research results show that pollution of water sources with plant protection products can pose a serious threat to aquatic ecosystems and drinking water The emergence of pesticides in surface water, wastewater and groundwater has led to finding appropriate measures to remove persistent pesticides Waste water pollution is pesticides have been treated by the above methods to ground or high cost and unstable performance Therefore, the development and selection of pesticide-contaminated water treatment technologies is an important Currently, the process of photocatalytic TiO2 is fixed based on the carrier material are interested in the field of environmental technology In terms of technology, the main objective of making up the carrier is TiO removal catalyst recovery stage after finishing treatment of polluted water The carrier typically used to attach TiO2 were glass, actived carbon and some polymers The main requirements is needed in a carrier attached TiO2 were heat resistance, has high specific surface area, high adsorption of pollutants, chemical inertness The methods commonly used for coating TiO2 on the carrier material: i) deposition method; ii) plasma coating method; iii) hydrothermal method, iv) sol-gel method In particular, sol-gel method combined with impregnation is a simple method that can be implemented in many laboratories in Vietnam to prepare TiO2/SiO2 Based on the review of the research materials, the thesis will focus on the following issues: - Provide optimal conditions for fabrication are impregnated TiO2 doped Fe, Co, Ni nanomaterials coated on SiO2 Determine the structural characteristics, the surface morphology of the material as well as the ability to absorb light and the ability to handle organic compounds (methylene blue) in the aquatic environment of the fabricated material - Evaluation of processing capability of the material has built in handles Paraquat, DDT in the aquatic environment by various light sources (UV, visible light) Test applied in handling DDT, paraquat in some form nuoctrong real environment CHAPTER 2: OBJECTIVES AND RESEARCH METHODS 2.1 The objectives of the thesis - TiO2 doped Fe, Co, Ni coated on SiO2 with the concentration Fe, Co, Ni metal in TiO2 catalysts ranges from to 9% - Plant protection chemicals: pesticide DDT and herbicide Paraquat Water samples containing PQ, DDT of varying concentrations (10 ppm, 20 ppm, 50 ppm) were mixed from standard and deionized water Real water samples were taken in Mai Chau district, Hoa Binh province for processing test PQ and collected at the stockpile of Thanh Luu (Nghe An), Hon Tro (Ha Tinh) for DDT treatment 2.2 Equipment - Scanning electron microscopy (SEM), Hitachi S-4800, National Institute of hygiene and epidemiology and SEM JSM 6010LA, AIST Institute, Japan to determine TiO2 grain size and TiO2 film thickness Component analysis of the EDX elements in the sample was also determined on this device - The XRD (D8 Advance - Bruker, Germany), which determines the crystal structure of the samples, was performed at the laboratory of the Department of Chemistry at the University of Natural Sciences - JEM1010 JEOL System at Chiao-Tung National University, Taiwan and TEM, Tecnal Osiris 200kV, FEI at AIST Institute, Japan used for HR-TEM imaging - Jasco V670 was used in the determination of absorption spectra at Faculty of Physics, Hanoi National University of Education with visible emission at wavelengths from 200 nm to 800 nm - Adsorption isotherm methods - the adsorption of nitrogen adsorption performed on 3FLEX at Faculty of Physics, Hanoi National University of Education - High performance HPLC - UV / VIS LC (Perkin Elmer) liquid chromatography analyzer used to determine the concentration of paraquat in water samples at a wavelength of 260 nm was conducted at the Institute of Environmental Technology, VAST - Shimadzu GC-ECD 2010 is used to measure the concentration of DDT and the UV5 VIS 2540, Shimadzu, Japan used to determine the methyl and green methyl concentrations in samples analyzed at the Institute of Environmental Technology, VAST 2.3 Research methods The research method used in the thesis is an experimental method that combines experiments with the use of reference materials to investigate the effect of fabrication conditions on the properties of materials and to present the to explain the relevant effects TiO2 doped Fe, Co, Ni coated on SiO2 is made based on sol-gel method combined with the impregnation method according to the following diagram: Figure 2.1 Process of synthesizing Ti1-xAxO2/SiO2 (A = Ni, Co, Fe) The photocatalytic activity of TiO2 doped Fe, Co, Ni samples were evaluated by the decomposition of MB, Paraquat and DDT in the dark, under UV and visible light Use grams of material to treat 250mL of test substance with initial concentration of 10 ppm The test environment has a pH value of 6,5 – 7,5 Processing system diagram is shown in Figure 2.4 Figure 2.4 Photocatalytic testing system in the laboratory 3.2.4 Evaluate the absorption of light The UV-vis spectrum was observed to investigate the optical properties of Ti 1xAxO2/silica gel (A=Fe, Co, Ni) Figure 3.25 presents the changes in the absorption spectra of Ti1-xAxO2/silica gel with the increase of metal dopant As shown in Fig 3.25, an obvious red shift to longer wavelength of the optical absorption edge on the metal doped TiO2 samples as compared to pure TiO2 sample was observed It clearly showed that increasing the Co, Fe, NI doping level makes the optical band gap reduce The evolution of this broad band shows that the Co ion generates new impurity states in the band gap of TiO2 These indicated that Fe, Co, Ni-doping could be a promising approach for increasing the catalytic activity Figure 3 Absorption spectra of Fe, Co, Ni doped TiO2/SiO2 sample 3.2.5 Evaluate the porosity of the material To estimate the porosity of the samples, the N2 adsorption – desorption isotherm was measured Figure 3.26 shows the hysteresis of Ti1-xAxO2/silica gel at 77 K The hysteretic shape of all samples is related to the Brunauer Type IV isotherm, which is characteristic of a mesoporous solid On the other hand, the isotherms of Co, Fe, Ni doped TiO2 were not different from the parent silica gel with specific surface area 143 m2/g, pore volume 0.57 cm3/g, pore size 154 Å 10 Figure 3.26 The hysteresis of Ti1-xAxO2/silica gel at 77 K 3.2.6 Evaluate the possibility of photocatalytic fabricated material We assessed the ability of the catalytic through decomposition experiment of MB in solution Fig 3.28 displays the degradation of MB using Fe-TiO2/SiO2 material at different times When the concentration of doped from 0% to 9% of the remaining MB concentration is 2.02; 2.94; 3.24; 6.18 and 7.74 ppm The 3% Fe doped sample showed the best performance in degradation MB The performance of Ti0.91Fe0.09O2/SiO2 sample was lower than Ti0,93Fe0,06O2/SiO2 ones maybe due to the lighter resistance even higher Fe contents Figure 3.28 Results of degrading MB of Ti1-xFexO2/SiO2 samples in dark condition (a), visible irradiation (b) with doping 0% (0), 1% (1), % (2), % (3), 9% (4) 11 Figure 3.29a is a graph showing the MB absorption of the Ti 1-xCoxO2/SiO2 sample system before illumination for 6h We found that for the samples in the dark after 3h, the MB concentration decreased negligible, almost unchanged In particular, Co 1% showed the strongest absorption and Co 9% showed the weakest absorption In particular, the photocatalytic potential of the Co 3% sample is best Thus, a concentration of 3% is the optimum concentration for a strong photocatalytic activity Figure 3.29 Results of degrading MB of Ti1-xCoxO2/SiO2 samples in dark condition (a), visible irradiation (b) with doping 0% (0), 1% (1), % (2), % (3), 9% (4) We assessed the ability of the catalytic through decomposition experiment of MB in solution Fig.4 displays the degradation of MB at different times The TiO2/SiO2 sample showed the highest adsorption of MB because of its large surface area It can be seen that Ni-doped TiO2 shows higher activity for degradation of MB in an aqueous solution compared to pure TiO2 Moreover, Ni2+ activated an important role in trapping the electrons and helps in charge separation, and therefore photocatalytic activity is comparatively good Ti0,93Ni0,06O2/SiO2 sample showed the best performance in degradation MB The performance of Ti0.91Ni0.09O2/SiO2 sample was lower than Ti0,93Ni0,06O2/SiO2 ones maybe due to the lighter resistance even higher Ni contents Figure 3.30 Results of degrading MB of Ti1-xNixO2/SiO2 samples in dark condition (a), visible irradiation (b) with doping 0% (0), 1% (1), % (2), % (3), 9% (4) 12 Remarks: The results of MB's performance testing of treatment doped materials show that: i) the ability of the photocatalyst Fe-doped sample to the largest but the adsorption capacity of the smallest ii) compared to doped Fe, Ni or Co doped samples are less photocatalytic but have better absorption capacity In which, Co-doped samples showed better photocatalytic efficiency than doped Ni samples 3.3 Evaluation of Paraquat treatment of Fe, Co, Ni doped TiO2 covered on SiO2 3.3.1 Effect of doped elements The photocatalytic activity of the TiO2 photocatalysts evaluated by the photocatalytic degradation of 10 ppm PQ under 365nm UV, visible light irradiation and dark condition is found in Fig 3.34 It seems that the PQ concentration decreases with progress of reaction, even in dark conditions for non-doped TiO2/silica gel In the case of the dark condition, it seems that the change of concentration almost stopped after 30 of circulation suggesting adsorption equilibrium However, under UV or visible light irradiation, the changes of PQ concentration resembled first order kinetics It seems that TiO2/silica gel had photocatalytic ability under UV-vis light irradiation For Co or Ni doped materials, the concentration of Paraquat was significantly reduced and the PQ concentration was reduced similarly under visible light conditions, 365 nm UV and even in the dark In contrast to Fe-doped material, the PQ concentration did not change even when illuminated by ultraviolet light 13 Figure Photocatalytic degradation profiles of PQ aqueous solutions obtained in a continuous reactor using TiO2 (A) and TiO2 doped 9% Ni (B), Co (C), Fe (D) covered on SiO2 On the other hand, the reduction of PQ was not dependent on light irradiation when the Co-doped TiO2 photocatalyst was used As shown in Table 1, the specific surface area of Co doped TiO2 photocatalyst was smaller than bare TiO2/silica gel photocatalyst However, as shown in Fig 8, the formation of final product of PQ with photocatalytic degradation was very small when compared with TiO 2/silica gel This result shows that the decrease of PQ concentration in the Ti 0.91Co0.09O2 system was caused by adsorption However, under UV or visible light irradiation, formation of NO3- was observed This final product of PQ was not observed under the dark condition One remarkable difference in photocatalytic tendency between TiO 2/silica gel and Ti0.91Co0.09O2 is the formation of NH4+ Under visible light irradiation, TiO2/silica gel photocatalyst only generated NH4+, while the Ti0.91Co0.09O2 photocatalyst generated only NO3- It can be considered that the NO3- formation is the result of NH4+ oxidation by photocatalysis Photocatalytic activity of Ti 0.91Co0.09O2 is lower than TiO2/silica gel, however, it is considered that the oxidation ability of Ti0.91Co0.09O2 is higher than TiO2/silica gel under visible light irradiation Therefore, Ti0.91Co0.09O2/silica gel photocatalyst showed the enhanced visible light photocatalytic activity to oxidize paraquat compared to bare TiO 2/silica gel This enhancement could result from the reduction of band gap energy The band gap of Ti0.91Co0.09O2/silica gel (2.64 eV) was smaller than bare TiO2/silica gel (3.32 eV), and hence under visible light irradiation, only electrons from the valence band of the Codoped sample could transfer into the conduction band This means that e - - h+ pairs 14 were created and allowed to generate hydroxyl radicals OH [6] The OH radical was extremely strong such that paraquat was oxidized to the final product NH4+ Figure Time course of photocatalytic degradation of PQ and formation of intermediates and/or final products by TiO2/silica gel in dark (a), visible light (b), UV light (c) and Ti0.91Co0.09O2/silica gel in dark (d), visible light (e), UV light (f) Remarks: i) TiO2 coated on silica gel shows good performance in treatment PQ in water environment when using 365 nm UV source activated The PQ concentration in the solution decreases due to both the adsorption and photocatalytic processes as illustrated in Figure 3.36 In this, the silica gel adsorbed strongly PQ, its concentration was reduced in the solution and the pollutant was bringed close to TiO crystals When TiO2 is irradiated with light of photon energy larger than the TiO band gap, electrons can be continuously excited from the valance band to the 15 conduction band to generate free electrons (e-) and holes (h+) The electrons react with oxygen and form superoxide radicals (O2.-), while the holes can combine with water (H2O) or hydroxyl ion (OH-) to generate hydroxyl radicals (OH.-) These radicals react easily to many organic compounds; breaking them down into byproducts Figure 36 Schematic description of adsorption / photocatalysis of TiO2/SiO2 ii) Doped samples are better able to adsorb than non-doped samples When the porosity of two materials is equal, their organic adsorption can be explained by point of zero charge - pzc The pzc value shown in Fig 3.37 shows that the dopant Co into the TiO2 crystalline lattice leads to an increase in the point of zero charge from pzc = 5.2 for non-doped TiO2/SiO2 to pzc = 6.6 for the Co 9% doped sample 9CoTiO2/SiO2 Therefore in a neutral environment, the surface of the material with the negatively charged hydroxyl groups can adsorb well the organic compounds which included positive charge as MB, PQ, DDT Figure 37 Graph of point of zero Figure 38 Fluorescence spectrum of charge of SiO2, TiO2/SiO2 and 9Co- 1Co-TiO2/SiO2 (4), 3Co- TiO2/SiO2 (3), TiO2/SiO2 6Co- TiO2/SiO2 (2) 9Co- TiO2/SiO2 (1) 16 Figure 39 Schematic description of the photocatalytic process of Co doped TiO iii) Doped samples has photocatalytically activity when using visible light sources, but photocatalysis was weaker than non-doped samples when using UV 365nm sources Co dopant also generates impurity levels below the conductor band, which reduces the band gap 2.6 eV (Figure 3.39) for the TiO2/SiO2 sample resulting in oxidation of PQ to inorganic nitrogen NO3- when using visible light In addition, when the doped concentration increases, it also increases the electron-hole recombination rate as shown in the fluorescence spectrum of figure 3.38, which results in the photocatalytic efficiency of the Co-doped sample less than that of the non-mixed sample when using UV 365nm light source 3.3.2 Evaluate the ability of Paraquat treatment in water environment with 10L/day test system a, Effect of initial concentration Pollutant concentration is an important parameter affecting the treatment of organic pollutants by photocatalysis As the concentration of pollutants increases, the adsorption rate and catalytic speed increase When the concentration of contaminant concentrations greater than the limit, the processing speed increased pollutant concentrations due to the OH radicals derived from the catalyst not increase To investigate the initial PQ concentration effect on the processing efficiency of 9CoTiO2/SiO2, solutions with initial PQ concentrations of 10 ppm, 20 ppm, 50 ppm were fed into the 10 L reaction system under visible light condition The results are shown in Fig 40 shows that when initial PQ concentration increases, the decomposition rate of PQ decreases This phenomenon may be from the initial concentration of PQ increases, it prevent the catalysts from forming the OH group leading to a decrease in photocatalytic efficiency 17 Figure 40 Effect of initial concentration on PQ treatment efficiency b, Effect of flow rate To investigate the effect of flow rate on the adsorption capacity of the material, operate the system with different flow rates (10mL/ph; 20 mL/ph 30mL/ph) was set up Test results for PQ at different flow rates are shown in Figure 3.41 The higher the flow, the lower the catalytic capacity of the material This may be because the exposure time of the material to the deoxidized element decreases Therefore, to achieve optimum processing efficiency, the 20mL/min flow rate is optimal for the treatment system Figure 41 Influence of flow rate to PQ removal c Ability to reuse The ability to reuse is one of the key parameters of the catalyst To evaluate the catalytic recyclability of the 9Co-TiO2/SiO2 material, the test with a visible light source, the initial PQ concentration of 10 ppm, the speed of 20 mL/min was investigated Results in Figure 3.42 shows that after times of use, the material is still good PQ treating capabilities that performance was 75% without reconstitution To the 8th cycle, the performance PQ began to decline to only 60% after 7pm testing 18 Figure 42 The ability to reuse of material in Paraquat treatment under fluorescent lighting conditions 3.4 Evaluation of DDT treatment of Fe, Co, Ni doped TiO2 covered on SiO2 3.4.1 The ability of DDT treatment TiO2/SiO2 material To evaluate the adsorption/photocatalytic activity of TiO2/SiO2 by treating pesticide p, p 'DDT with an initial concentration of ppm, the material weight 10 g, the experimental conditions were set similarly as in the Paraquat treatment Figure 3.43 shows the concentration-dependent p, p’ DDT over time and evaluate reaction rate (inset) The results showed that p, p’ DDT concentrations were significantly reduced After hour, the p, p’ DDT treatment efficiency of TiO2/SiO2 was 78% in dark conditions and 97% in UV 365nm Thus, the concentration of p, p 'DDT was stronger reduction in UV conditions The cause of this phenomenon can be explained as: (i) material carrying particles SiO2 express adsorption capacity well p, p’ DDT due to electromagnetic interaction is like the case of MB, Paraquat led to the concentration of p, p' DDT reduced as the exponentially rule in both condition with and without UV; (ii) TiO2 is capable of photocatalytic decomposition of p, p' DDT Therefore, during the first part of the experiment, both photocatalytic and photocatalytic phenomena occurred simultaneously causing the concentration of p, p' DDT to decrease faster with UV 365nm 19 Figure 43 Ability to treating DDT of TiO2/SiO2 in dark conditions (1) and UV 365nm (2) Information on intermediate products during photocatalytic processing of DDT is determined using the chromatogram shown in Figure 3.44 Chromatogram shows the existence of two peaks in the retention time of 12.1, 12.7 minutes respectively two compounds are chlorobenzene, chlorophenol Therefore, it can be confirmed that DDT is also decomposed by photocatalysis produce two characterized products which were chlorobenzene and chlorophenol Figure 44 Chromatogram p, p 'DDT in water samples after UV 60 minutes illumination 3.4.2 The ability of DDT treatment Co doped TiO2/SiO2 material Effect of doping to the ability to decomposed pesticide p, p' DDT was tested with samples Co doped 9% 9Co-TiO2/SiO2 In particular, the initial concentration was ppm, the amount of material used was g Figure 3.45 shows the dependence of the p, p' DDT concentration over time on materials in visible and illuminated lighting conditions The results showed that only p, p' DDT adsorption on the materials was occured In particular, SiO2 exhibits the strongest adsorption capacity of p, p' DDT, and the incorporation of the catalyst onto SiO decreased the adsorption ability of material The cause could be the introduction TiO2 or Co doped TiO2 on SiO2 makes reduces the specific surface area resulting in reduced adsorption capacity In addition, with or without visible light, the rate of decline in the concentration of p, p 'DDT in solution does not differ for SiO2, TiO2/SiO2 and 9Co-TiO2/SiO2 This suggests that photocatalytic activity does not occur with visible light 20 Figure 45 The ability to adsorb (a) and capable of treating DDT using SiO2 (b), TiO2/SiO2 (c), Co doped TiO2/SiO2 (d) 3.5 Testing of Paraquat, DDT in reality water samples 3.5.1 Paraquat treatment Permissible limits for Paraquat in drinking water are μg/L (EPA, US Environmental Protection Agency), 10 μg/L (WHO), 0.1 μg/L (European) In Vietnam, this indicator is not in the standard QCVN 01: 2009/BYT on the quality of drinking water Meanwhile, QCVN 8:2011/BTNMT (Surface Water Quality) column A1, Paraquat permissible concentration is 900 μg /L Water samples in Mai Chau, Hoa Binh province in five communes of Cu Pheo, Pieng Co, Tram, Mai Hich and Van Mai were collected to determine the concentration of Paraquat in the reality environment Sampling location maps are described in Figure 3.46 Samples were taken at the time before and after spraying herbicide The samples were collected in L brown glass bottles and transferred to the laboratory Total samples were 68 samples The results of the concentration analysis shown in Figure 3.47 show that paraquat is most present in samples at concentrations of 10-150 μg/L Some samples of water in the villages CP, PV, PQ levels are 10-15 times higher than other villages in both sampling periods 21 Figure 46 Map of sampling locations in villages of Cú Phèo, Piềng Co, Xăm Khoe, Mai Hịch and Van Mai in Mai Chau district, Hoa Binh province 180 23/5/2016 22/5/2017 160 140 Paraquat (µg/L) 120 100 80 60 40 20 Vị trí lấy mẫu Figure 47 Paraquat concentration in the samples examined in two rounds (CP: Cún Phèo; XK: Xăm Khoe; MK: Mai Hịch; PV: Piềng Cò) From the results of chemical analysis of herbicide, the thesis has taken samples for testing represent material handling have made The PQ treatment capacity for the reality water sample was tested under optimum conditions on the 10L test system: 9Co-TiO2/SiO2 materials; flow rate of 20 mL / min, using sunlight The results of Paraquat treatment (Fig 3.48) in the Mai Chau water sample using 9Co-TiO2/SiO2 material under 10L natural light showed that PQ concentration of 200μg/L after hours was removed The actual sample time is smaller than the false sample due to the smaller concentration Therefore, the material can be reused more 22 Figure 48 PQ decomposition with 9Co-TiO2/SiO2 material using sunlight 3.5.2 DDT treatment DDT treating capability for real samples was performed on a 10L system using Co doped 9Co-TiO2/SiO2 under fluorescent light conditions In particular, the real water sample is filtered before it enters the system The results in table 3.11 show that after cycles, the treatment efficiency of the material for the water sample in the pesticide inventory was 99.3% Thus, for the sample material is still showing good processing ability Table 11 The concentrations of DDT remaining after the treatment cycle Diễn Châu Depot, ppm Thạch Lưu Depot, ppm Pre-treatment 4.96 4.28 Cycle 0.035 0.032 Cycle 0.036 0.034 Cycle 0.038 0.033 Cycle 0.037 0.038 Cycle 0.035 0.033 23 Chapter CONCLUSIONS Have found that the optimum conditions for fabrication TiO2 immobilized on silica were 60 minutes soaked silica in sol, 500oC annealed and times coating Have been successfully applied metal (Ni, Co and Fe) in TiO2 crystal It has no significance of the influence of transition metal doping on anatase TiO2 structure The dopants are evenly distributed in the sample without clumping phenomenon When doped metal concentrations increased from 0% to 9%, the width of the band gap of 3.3 eV to form reduced from 3.1 eV (for doped Ni), from 3.3 eV to 2.6 eV (for doped doping) and 3.3 eV to 2.8 eV (for Fe doped) Have assessed the structure, morphology, crystallinity and porosity of TiO2/SiO2 and (Ni, Fe and Co) doped TiO2/SiO2 materials TiO2 crystal size was 10 nm and existed in the single Anatase phase Ni, Fe and Co) doped TiO 2/SiO2 materials have a specific surface area of 140 m2/g and the Ni, Fe and Co metals are evenly distributed in TiO2 crystals Having assessed the ability of the material photocatalytic TiO2/SiO2 doped (Ni, Fe and Co) for methylene blue compound, paraquat and DDT in the laboratory scale Selection of Co 9% doped rate in TiO2/SiO2 material is optimal when using visible light TiO2/SiO2 material when Co and Ni doped gives better adsorption capacity but the photocatalytic ability is in contrast to TiO2/SiO2 doped Fe material When using fluorescent light source, Co- TiO2/SiO2 material is able to thoroughly handle paraquat at a concentration of 10 ppm after 1.5 hours Intermediate products in PQ decomposition process are NH4 + when using TiO2/SiO2 and NO3materials when using materials 9Co- TiO2/SiO2 With 365nm UV light source, DDT decomposed, creating intermediate products as chlorophenol and using materials clobenzen TiO2/SiO2 Designed a 10L / day treatment system, tested the ability to handle paraquat in surface water samples in some communes, Mai Chau and Hoa Binh districts The post-treatment PQ concentration is below the permitted standard QCVN 8: 2011 / BTNMT 24 ... of treatment paraquat and ddt in water environment using Fe, Co, Ni doped TiO2 nano material” was studied The purpose of the study - The Fe, Co, Ni, Ti was applied into the TiO2 nanocrystals... of Paraquat and DDT pollution in the water environment in the world and in Vietnam; ii) Methods of treatment Paraquat, DDT; iii) pure TiO2 and doped TiO2; iv) Methods of fabrication TiO2 nanoparticles... with the concentration Fe, Co, Ni metal in TiO2 catalysts ranges from to 9% - Plant protection chemicals: pesticide DDT and herbicide Paraquat Water samples containing PQ, DDT of varying concentrations